The present invention relates to shock detectors and, more particularly, to a low-power shock detector for measuring intermittent shock events.
A significant requirement for mobile tracking units used in vehicles which generally lack a power source, such as freight railcars, shipping containers and the like, is to have relatively low electrical power consumption characteristics. Mobile tracking units used in a power-starved environment must be substantially power efficient in order to provide reliable and economical operation. Typically, the mobile tracking unit includes a navigation set, such as a Global Positioning System (GPS) receiver or other suitable navigation set, responsive to navigation signals transmitted by a set of navigation stations which can be either space- or earth-based. In each case, the navigation set is capable of providing data indicative of the vehicle location based on the navigation signals. In addition, the mobile tracking unit can include a suitable electromagnetic emitter for transmitting to a remote location the vehicle position data and other data acquired with sensing elements in the vehicle. For presently available mobile tracking units, use of a motion sensor, such as an accelerometer or shock detector, has been suggested for detecting shock or impact events which the vehicle encounters during routine use. However, no suggestion has been made of techniques for substantially reducing the power consumption of such shock detector. Thus, it is desirable to provide an improved shock detector that allows for economical and reliable operation in a power-starved environment. It is also desirable to provide a shock detector that, notwithstanding its relatively low-power consumption over presently available shock detectors, is capable of measuring any shock event in a substantially accurate manner in order to provide to users meaningful information about the shock events.